From 074785cea106179cb3305637055ab0a009ca74f2 Mon Sep 17 00:00:00 2001 From: Peter Bengtsson Date: Tue, 8 Dec 2020 14:42:52 -0500 Subject: initial commit --- .../web/api/htmlcanvaselement/todataurl/index.html | 157 +++++++++++++++++++++ 1 file changed, 157 insertions(+) create mode 100644 files/pt-br/web/api/htmlcanvaselement/todataurl/index.html (limited to 'files/pt-br/web/api/htmlcanvaselement/todataurl/index.html') diff --git a/files/pt-br/web/api/htmlcanvaselement/todataurl/index.html b/files/pt-br/web/api/htmlcanvaselement/todataurl/index.html new file mode 100644 index 0000000000..503f9cb636 --- /dev/null +++ b/files/pt-br/web/api/htmlcanvaselement/todataurl/index.html @@ -0,0 +1,157 @@ +--- +title: HTMLCanvasElement.toDataURL() +slug: Web/API/HTMLCanvasElement/toDataURL +tags: + - API + - Canvas + - HTMLCanvasElement + - Imagens +translation_of: Web/API/HTMLCanvasElement/toDataURL +--- +
+
+
{{APIRef("Canvas API")}}
+
+
+ +

O método HTMLCanvasElement.toDataURL() retorna uma data URI, contendo uma representação da imagem no formato especificado pelo parâmetro type (por padrão, esse valor é PNG). A resolução da imagem retornada é de 96 dpi.

+ + + +

Sintaxe

+ +
canvas.toDataURL(type, encoderOptions);
+
+ +

Parâmetros

+ +
+
type {{optional_inline}}
+
Uma {{domxref("DOMString")}} indicando o formato da imagem. Por padrão, o formato definido é image/png.
+
encoderOptions {{optional_inline}}
+
Um {{jsxref("Number")}} entre 0 e 1, indicando a qualidade da imagem solicitada pelo tipo image/jpeg ou image/webp.
+ Se esse argumento for outro valor que não de 0 a 1, então o valor padrão (0.92) será usado. Outros valores serão ignorados.
+
+ +

Valor retornado

+ +

Uma {{domxref("DOMString")}} contendo a data URI solicitada.

+ +

Exemplos

+ +

Dado este elemento {{HTMLElement("canvas")}}:

+ +
<canvas id="canvas" width="5" height="5"></canvas>
+
+ +

Você poderá capturar a data-URL do canvas com as seguintes linhas:

+ +
var canvas = document.getElementById('canvas');
+var dataURL = canvas.toDataURL();
+console.log(dataURL);
+// "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNby
+// blAAAADElEQVQImWNgoBMAAABpAAFEI8ARAAAAAElFTkSuQmCC"
+
+ +

Defindo a qualidade de imagens jpeg

+ +
var fullQuality = canvas.toDataURL('image/jpeg', 1.0);
+// data:image/jpeg;base64,/9j/4AAQSkZJRgABAQ...9oADAMBAAIRAxEAPwD/AD/6AP/Z"
+var mediumQuality = canvas.toDataURL('image/jpeg', 0.5);
+var lowQuality = canvas.toDataURL('image/jpeg', 0.1);
+
+ +

Exemplo: Alterando imagens dinamicamente

+ +

Você poderá utilizar esta técnica em associação com os eventos do mouse para alterar dinamicamente uma imagem (escala de cinza vs. cor, neste exemplo):

+ +

HTML

+ +
<img class="grayscale" src="myPicture.png" alt="Description of my picture" />
+ +

JavaScript

+ +
window.addEventListener('load', removeColors);
+
+function showColorImg() {
+  this.style.display = 'none';
+  this.nextSibling.style.display = 'inline';
+}
+
+function showGrayImg() {
+  this.previousSibling.style.display = 'inline';
+  this.style.display = 'none';
+}
+
+function removeColors() {
+  var aImages = document.getElementsByClassName('grayscale'),
+      nImgsLen = aImages.length,
+      oCanvas = document.createElement('canvas'),
+      oCtx = oCanvas.getContext('2d');
+  for (var nWidth, nHeight, oImgData, oGrayImg, nPixel, aPix, nPixLen, nImgId = 0; nImgId < nImgsLen; nImgId++) {
+    oColorImg = aImages[nImgId];
+    nWidth = oColorImg.offsetWidth;
+    nHeight = oColorImg.offsetHeight;
+    oCanvas.width = nWidth;
+    oCanvas.height = nHeight;
+    oCtx.drawImage(oColorImg, 0, 0);
+    oImgData = oCtx.getImageData(0, 0, nWidth, nHeight);
+    aPix = oImgData.data;
+    nPixLen = aPix.length;
+    for (nPixel = 0; nPixel < nPixLen; nPixel += 4) {
+      aPix[nPixel + 2] = aPix[nPixel + 1] = aPix[nPixel] = (aPix[nPixel] + aPix[nPixel + 1] + aPix[nPixel + 2]) / 3;
+    }
+    oCtx.putImageData(oImgData, 0, 0);
+    oGrayImg = new Image();
+    oGrayImg.src = oCanvas.toDataURL();
+    oGrayImg.onmouseover = showColorImg;
+    oColorImg.onmouseout = showGrayImg;
+    oCtx.clearRect(0, 0, nWidth, nHeight);
+    oColorImg.style.display = "none";
+    oColorImg.parentNode.insertBefore(oGrayImg, oColorImg);
+  }
+}
+ +

Especificações

+ + + + + + + + + + + + + + + + + + + + + + + + +
SpecificationStatusComment
{{SpecName('HTML WHATWG', "scripting.html#dom-canvas-todataurl", "HTMLCanvasElement.toDataURL")}}{{Spec2('HTML WHATWG')}}No change since the latest snapshot, {{SpecName('HTML5 W3C')}}
{{SpecName('HTML5.1', "scripting-1.html#dom-canvas-todataurl", "HTMLCanvasElement.toDataURL")}}{{Spec2('HTML5.1')}}
{{SpecName('HTML5 W3C', "scripting-1.html#dom-canvas-todataurl", "HTMLCanvasElement.toDataURL")}}{{Spec2('HTML5 W3C')}}Snapshot of the {{SpecName('HTML WHATWG')}} containing the initial definition.
+ +

Compatibilidade entre navegadores

+ + + +

{{Compat("api.HTMLCanvasElement.toDataURL")}}

+ +

Veja também

+ + -- cgit v1.2.3-54-g00ecf